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Date:      Sat, 22 Sep 2012 09:35:45 +0200
From:      "O. Hartmann" <ohartman@zedat.fu-berlin.de>
To:        freebsd-current@freebsd.org
Subject:   Re: More kernel performance tests on FreeBSD 10.0-CURRENT
Message-ID:  <505D6A51.7090808@zedat.fu-berlin.de>
In-Reply-To: <505CDE9C.3060504@andric.com>
References:  <505CDE9C.3060504@andric.com>

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Am 09/21/12 23:39, schrieb Dimitry Andric:
> Hi all,
>=20
> As a followup to my previous post about the performance of FreeBSD 10.0=

> kernels compiled with different compilers (clang and gcc), I did anothe=
r
> series of tests, now on a more modern machine (Core i5-based).  I also
> tested the performance with different compiler optimization settings.
>=20
> The attached text file[1] contains more information about these tests,
> performance data, and my conclusions.  Any errors and omissions are als=
o
> my fault, so if you notice them, please let me know.
>=20
> The executive summary: GENERIC kernels compiled with clang 3.2 are agai=
n
> a little faster than those compiled with gcc 4.2.1.  For gcc, compiling=

> with -O2 also gives a slightly faster kernel than with -O1, but for
> clang there is no measurable difference between those flags.
>=20
> Again, many thanks to Gavin Atkinson for providing the required
> hardware.
>=20
> -Dimitry
>=20
> [1]: Also available at:
> <http://www.andric.com/freebsd/perftest/perftest-kernel-2012-09-21a.txt=
>


At least one can say FreeBSD does not suffer from performance drain
using the cutting edge clang 3.2 compared with a gcc 4.2.1 compiler, the
echo from the past.

Dimirty, are you planning also to benchmark clang 3.2 versus gcc 4.8.0?
=46rom the development point of view, such a benchmark would be more
natural, but I do not know whether the kernel sources are gcc
4.8-friendly and would allow such a test.

What is about optimization level "-O3" and architectural recognition via
"-march=3Dnative"?

Neverthelesse, thanks.

oh







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